In oceanographic, seismographic and related studies, it is well known that vessels are used to move across the surface of the water discharging acoustic impulses. These impulses are then received by related instruments to provide data for the studies. The devices used to discharge the acoustic impulses are commonly called acoustic impulse generators and provide acoustic energy in and through sea water and other fluid media.
Typically, these generators are immersed in the fluid media and have a movable striker for impacting against a surface of the generator. Although many fluids are used to move the striker, commonly, a gas charge is provided to one side of the striker for moving it against the surface. Because the generator is immersed, it has been very difficult to prevent damage to the striker from the liquid media. Moreover, the intensity of the acoustic signal generated depends on the pressure of the gas charge. Thus, multiple large compressors are supported by the vessels to provide these high gas pressures, such as 2000 psi. Because there are multiple compressors used and they are large, substantial valuable space is used in the vessels for the compressors.
Accordingly, it is a primary object of the present invention to provide an acoustic impulse generator which may be immersed in a liquid media without harmful damage to movable components therein.
A further object of the present invention is to provide an acoustic impulse generator that generates acoustic impulses in a fluid media using a relatively low gas pressure.
A further object of the present invention is to provide an acoustic impulse generator that needs less space in vessels for compressors than prior art generators.
A further object of the present invention is to provide an acoustic impulse generator that uses a diaphragm covering a passageway in a housing to prevent the passage of liquid from the fluid media into the housing.
A further object of the present invention is to provide an acoustic impulse generator which has a diaphragm constructed so that no stresses develop in the diaphragm when the diaphragm is moved.
A further object of the present invention is to provide an acoustic impulse generator having a firing chamber attached to a housing for channeling a quantity of liquid through a nozzle, the nozzle being constructed to generate the acoustic impulse into liquid outside of the firing chamber.
In accordance with the invention, an acoustic impulse generator used in a liquid media, such as sea water, is disclosed. The generator includes a housing forming a gas chamber having an inlet end with a passage communicating with the gas chamber for receiving a charge of gas, an outlet end with a passage communicating with the gas chamber for exhausting gas from the gas chamber and a passageway in the outlet end. A piston is slidably disposed within the gas chamber and has a head for receiving the charge of gas and a rod attached to the head for moving through the passageway. A firing chamber is attached to the housing for channeling a quantity of liquid through a nozzle into liquid located outside the firing chamber and is constructed to generate the acoustic impulse into the outside liquid. A diaphragm is disposed between the housing and the firing chamber covering the passageway to prevent the passage of liquid through the passageway from the firing chamber to the gas chamber and a quantity of liquid is displaced from the firing chamber in response to movement of the piston and diaphragm.